1. Field of Industrial Utilization
The present invention relates to a roller bearing to place two members relatively in an infinite rectilinear motion by endlessly circulating cylindrical rollers or long cylindrical rollers which are inserted between two members. More specifically it relates to a bearing for an infinite rectilinear motion of what is called a parallel roller type, wherein cylindrical rollers in the track faces of rolling rows of the rollers are so arranged that axes of the rollers are parallel with each other, and are directed in the same direction; and said roller bearing is improved in the direction change passage for causing rollers in the track to change their direction and leading them to a return passage.
2. Prior Art
In the type of arrangement of rollers in a track face for this kind of roller bearings for an infinite rectilinear motion, there can be classified the cross roller type wherein rollers are so arranged that axes of adjacent rollers may cross at right angles with each other, and the parallel roller type wherein rollers are so arranged that axes of adjacent rollers are directed in the same direction.
In the cross-roller-type-bearing, two rows of endlessly circulating rollers (endless circulation passage) are sufficient for enabling rollers to carry loads burdened from every direction, hence roller bearings having a relatively small sectional height can be manufactured in this type.
The parallel-roller-type-bearing, however, requires at least four rows of endless circulation passages for rollers, in order to enable rollers to carry loads burdened from every direction. This bearing type has many defects in that the width and height of the bearing will become too great (for example, see Japanese Patent Application No. 248789-1983), or that the construction of members of the endless circulation passage will become complicated (for example, see Japanese Patent Application No. 94552-1981) etc., thus leaving problems in miniaturization and costs for construction.
The following is description given with reference to FIG. 7 of defects of bearings of conventional parallel roller type. Since FIG. 7 is symmetric with the center line, symbols are given for only members at the left side of the center line. In mounting the casing 11 astride the track rail 12, rollers 13 and 13A, when viewed in the sliding direction, are inclined, for example, at 45 degrees relative to the sliding plane for the bearing, or to the horizontal plane, and the rollers are so arranged that extension lines (not shown) of each axis (rotation axes) of the rollers 13 and 13A may cross at right angles with each other, in order for the rollers to be able to carry loads burdened from every direction. Return passages 14, 14A are formed in the casing 11, and the two track grooves in which rollers 13 and 13A exist and the return passages 14 and 14A are communicated with each other respectively by direction change passages 15 and 15A.
In order for the rollers to be able to move smoothly in the track grooves, the direction change passages 15 and 15A, and the return passages 14 and 14A, each of the return passages 14 and 14A needs to be formed at a location inclined by 45 degrees, from the two truck grooves relative to the sliding plane for the bearing (horizontal plane). Hence, the height h.sub.1 of the casing 11 of such a parallel-roller-type becomes very great as compared with a cross-roller-type-bearing. That is, in the conventional parallel roller type, a sectional height of a bearing will inevitably be great due to motional characteristics of the rollers, and it leads to increase in number of parts thereof, as well as in the manufacturing cost.
To reduce the height of the casing, there has been proposed formation of the track grooves, the direction change passages 15 and 15A, and the return passages 14 and 14A in a crosswisely arranged relationship, as shown in FIG. 8. In this case, the height h.sub.2 of the casing 11 can be made smaller than in the case of FIG. 7 (the height h.sub.1). It requires, however, very complicated and difficult working processes to work and form the inside of the casing 11 in the manner such that the direction change passages 15 and 15A may cross with each other without any interference between them, further highly accurate work thereof is difficult, and the manufacturing cost will also be increased.